Polyvinylpyrrolidone (PVP) is a well known synthetic polymer having properties which make it suitable for many pharmaceutical, cosmetic, clinical and industrial uses and applications. One of its most important properties is its ability to form complexes with a large variety of compounds, such as iodine, phenolic materials, and dyes.
The PVP polymer has a linear hydrophobic hydrocarbon backbone wherein every alternate carbon atom is bonded to the nitrogen atom of the carboimide group of the hydrophilic 2-pyrrolidone ring as illustrated by the structural formula ##STR3##
The unique balance between the hydrophobic and hydrophilic segments of the polymer accounts for its unique characteristics. The carboimide moiety of the pyrrolidone is a polarizable group which makes the lactam eminently susceptible to hydrogen bonding and complex formation. There is also evidence that the hydrophobic backbone participates in various types of attractive forces, such as van der Waals forces, which also participate in complex formation. In addition, the pyrrolidone ring complexes with unsaturated hydrocarbons such as substituted or unsubstituted benzene naphthalene, anisole, methyl salicylate, etc., through a charge-transfer system.
Although the complexes of PVP are stable, the intensity of attractive forces between the PVP polymer and other molecules, such as iodine and phenolics, depends to a large extent on the steric properties surrounding the sites where such forces exist. Steric crowding, between the pyrrolidone lactam ring and the hydrocarbon backbone alter the intensity of attractive forces, and lower the stability of the complex. An examination of the structure of polyvinylpyrrolidone shows that steric crowding exists between the amide functional group of the lactam and the hydrocarbon backbone. This is due to the fact that the polymer is derived from vinylpyrrolidone monomer and the hydrocarbon backbone is bonded directly to the nitrogen atom of the lactam ring. Because of this crowding effect, certain molecules having a bulky nature fail to complex, or exibit limited complexing, along the PVP chain.
Accordingly, it is an object of this invention to provide lactam monomers which have considerably reduced steric hindrance between the lactam amide and the hydrocarbon backbone in polymers formed therefrom.
It is another object of this invention to produce a polymer of the present compounds which are capable of complexing with a wide variety of molecules, including molecules having a bulky structure.
Still another object of the invention is to provide a compound which is highly reactive as an intermediate for the formation of numerous addition products.
Yet another object of the invention is to provide a process for the homopolymerization and copolymerization of the present compounds by a commercially feasible and economical process.
These and other objects of the invention will become apparent from the following description and disclosure.